An optical waveguide mixes and directs light emitted by one or more light sources, such as one or more light emitting diodes (LEDs). A typical optical waveguide includes three main components: one or more coupling elements, one or more distribution elements, and one or more extraction elements. The coupling component(s) direct light into the distribution element(s), and condition the light to interact with the subsequent components. The one or more distribution elements control how light flows through the waveguide and is dependent on the waveguide geometry and material. The extraction element(s) determine how light is removed by controlling where and in what direction the light exits the waveguide.
In order for an extraction element to remove light from the waveguide, the light must first contact the feature comprising the element. By appropriately shaping waveguide surfaces, one can control the flow of light across the extraction feature(s). Selecting the spacing, shape and other characteristic(s) of the extraction elements affects the appearance of the waveguide and its resulting angular distribution of emitted light and efficiency. However, waveguide shape and extraction feature characteristics are generally fixed, thereby producing a static illuminance distribution pattern of the lighting device. Alteration of the illuminance distribution pattern, therefore, requires the lighting device to be adjusted via one or more means external to the device, such as by an individual manually moving, adding or removing optical element(s) of the lighting device. Such external modification can be time consuming and precludes real-time adjustments in response to changes in the lighting environment.